Electrolytic condenser containing monoethanolamine



Patented Sept. 1,1, 1934 UNITED STATES PATENT OFFICE- ELECTROLYTICCONDENSER CONTAINING MONOETHANOLAMINE No Drawing. Application December10, 1932, Serial No. 646,742

Claims.

This invention relates to condensers of the type wherein an electrolyticfilm is maintained on the surface of armatur-es or electrodes, such asaluminum, and employing an. electrolyte in the form 5 of a heavy liquid.

I have discovered that an improved condenser of this type may be made bythe use of monoethanolamine in combination with boric acid and glycol orsimilar substance, that is, carbon compounds having similarly orientatedhydroxyl groups on adjacent carbon atoms.

As an example of the electrolyte I mix the following ingredients in theproportions indicated:

Parts by weight Monoethanolamine 1 Glycol 5 Boric acid 5 In my copendingapplication Ser. No. 538,400, filed May 18, 1931, I have described anelectrolyte embodying triethanolamine, boric acid and a material such assucrose, glycol or glycerol. Glycol is preferred in the present formulabecause paste containing it has a lower viscosity, lower power factor,and higher conductivity. I find that if ordinary sucrose is used as a,polyhydroxyl compound caramelization is apt to take place. Iaccordingly prefer glycol.

It shou d be noted that the molecular weights given in the abovespecific example are approximately identical. Consequently in the ratiochosen nearly all the boric acid and glycol will unite to formglycoboric acid, about one-fifth of which compound is neutralized by theethanolamine.

The above mixture is heated to boiling and the boiling continued to atemperature between 125 and 130 C. in order to drive off part of thewater originaly present and that liberated by the reactions in theelectrolyte. The reaction produces glycoboric acid andmonoethanolammonium glycoborate. When this temperature is reached, Ithen immerse therein the electrolytic condenser rolls of a type wellknown in the art and impregnate these rolls with the electrolyte.Instead of the ordinary type of roll, I may employ condenser rolls withscratched-brushed anodes and narrow cathodes as described in mycopending application Ser. No. 623,925, filed July 22, 1932.

The condenser rolls so impregnated may be formed in the electrolyte soprepared in a manner well known to the art; i. e. by applying a highvoltage to the condenser terminals through a resistor of suificientmagnitude. I find that I am able to form such condensers from a 510 voltD. C. line through a 5000 ohm resistor, for two condensers, up to aleakage of approximately 0.5-1.0 ma per condenser at 500 volts inapproxi mately 24 hours or less. A condenser so formed has the capacityrequired and an extraordinarily low power factor. In fact I haveobtained power factors in this way under 3%. The leakage characteristicsof the condensers so formed are also satisfactory.

Although I have described above a ratio of 5 glycol to 1monoethanolamine to 5 boric acid, a composition containing a smallerratio of monoethanolamine may also be used but the resistance of themass is thereby increased. Similarly a larger ratio of ethanolamine maybe used but the formation time is thereby somewhat increased.

Although I have described specifically the use of monoethanolamine, Imay incorporate some triethanolamine or some other highly substitutedalcoholamine, such as in some instances being desirable since it yieldsa mass of higher viscosity. I have found in general that the use ofmonoethanolamine is desirable because monoethanolammonium ion is smallerthan triethanolammonium ion and associates fewer ions with itin-solution. Its ionic mobility consequently suffers but little changewhen the temperature is lowered and therefore change in temperature hasbut limited effect on the power factor and capacity. The condenserprepared with this electrolyte has improved shelf-life characteristicsin addition to the lower power factor mentioned, better performance atlow temperatures and lower formation time.

In the claims wherethe expression glycol is employed, it is to beunderstood that it includes glycerin and other equivalents therefor.

In the manufacture of condensers, if the electrolyte mass becomesinefiicient because of the loss of too much water, water may be addedthereto to bring it back to its original consistency.

I claim:

1. An electrolytic condenser of the class described having an armatureof the film-forming type and an electrolyte of glycol, monoethanolamineand boric acid combined in the approximate ratio of 5 to 1 to 5 parts byweight.

2. An electrolytic condenser of the class described having an armatureof the film-forming type and an electrolyte of monoethanolammoniumglycoborate and glycoboric acid.

3. An electrolytic condenser of the class described having an armatureof the film-forming 110 scribed having an armature of the film-formingtype and an electrolyte consisting of glycol, boric acid and material toincrease the viscosity there of selected from the group monoethanolamineand triethanolamine. I

V MILTON BERGSTEINL

